1. Field of the Invention
The present invention relates generally to wireless networks and communication. Specifically, the preferred embodiments of the present invention relate to methods and systems for providing remote antennas to extend the coverage area and call capacity of a spread-spectrum based wireless network.
2. Description of the Related Art
The field of spread spectrum, wireless communication has been active for over a decade. For instance, the advantages of an exemplary code division multiple access (CDMA) system are described in U.S. Pat. No. 4,901,307 issued Feb. 13, 1990 to K. Gilhousen et al. Since then, a number of techniques have been proposed for compensating the multiple access interference (MAI) associated with spread spectrum wireless systems. As conventionally known in the art, MAI is a significant noise source limiting the practical capacity and performance of second generation, spread-spectrum based wireless services, such as one based on CDMA digital transmission.
The foremost technique for compensating MAI and ensuring reliable communication is to control the transmitted power from both the mobile station and the base station. Several examples of this technique are described in U.S. Pat. Nos. 6,119,010, 6,118,983, and 6,104,933. A second technique relies on controlling the patterns of the receiving and transmitting antennas. By dividing the service area into independent sectors or adaptively nulling interferers (so-called space time adaptive processing), MAI from other users that are directionally resolvable may be substantially reduced. U.S. Pat. Nos. 6,101,399, 6,078,823, and 5,953,325 are examples of this technique. Yet another technique utilizes complex, non-linear algorithms in the receiver to concurrently estimate the signals from a multitude of users, as shown in U.S. Pat. Nos. 6,081,516, 6,014,373, and 5,956,333). Termed multi-user detection (MUD), such approaches require extensive computational resources at the receiver and, as such, are suitable for use on the uplink (at the base station) but not on the downlink (at the mobile).
The use of signal repeaters also has been proposed in the field of spread spectrum, wireless communication. As conventionally known in the art, repeaters are basically devices that amplify or regenerate the data signal in order to extend the transmission distance. The industry standard organization for next generation, i.e. third generation (3G), CDMA systems has included one implementation of repeaters in its standard. Termed Opportunity Driven Multiple Access (ODMA), that configuration is discussed in the Third Generation Partnership Project Technical Report 25.924 version 1.0.0. A number of patents, such as U.S. Pat. Nos. 6,108,364 and 5,875,209, also relate to repeaters. Additionally, there are patents, such as U.S. Pat. Nos. 5,936,754, 5,867,485, and 5,809,422, that propose remote emitters linked to the base station via means other than an in-band radio frequency (RF) transmission to support both the uplink and downlink.